The effects of an incisal bite plane on rat submandibular glands

The submandibular glands of rats subjected to application of an incisal bite plane became slightly, but not significantly, enlarged. However, in comparison with control animals, they secreted additional proteins identical with those secreted by glands enlarged by periodic incisor amputation or chronic isoproterenol treatment.     

Fluoride in human saliva after ingestion of aluminium chloride and sodium fluoride or sodium monofluorophosphate

Four fasting adults were given 5 mg of F as NaF or Na₂PO₃F without and with 3.5, 7.1 or 14.2 mg Al as AlCl₃. Each salt combination was administered in 1 ml aqueous solution, and swallowed in a gelatine capsule with 10 ml of water. Samples of paraffin-stimulated whole saliva, collected before and at short intervals over a period of 3 hr after the administration, were analysed for total and ionic F. After ingestion of F without Al, there was a rapid increase in salivary F, with peak levels of about 0.2 ppm attained after approximately 50 min. When F was ingested with Al, the rate of increase of salivary F was depressed, and peak levels were reduced. This effect was slight for 3.5 mg Al, somewhat greater for 7.1 mg, and marked for 14.2 mg. No Al was detected in the saliva by spectrographic analysis. Fluorine given as PO₃F^2? gave a slower rise in salivary F, and lower peak levels in 3 of 5 subjects than NaF, but the response to Al was similar. Only ionic F was detected in whole saliva and in samples of parotid saliva collected after ingestion of PO₃F^2?. It is concluded that Al interferes with gastrointestinal absorption of F by forming poorly absorbable Al-F complexes, and that PO₃F^2? is subjected to hydrolysis prior to absorption of F. The findings suggest that the Al normally present in food and beverages may affect gastrointestinal absorption of F.     

Metastasis of adenoid cystic carcinoma of the mandible to the Gasserian ganglion.

A case of adenoid cystic carcinoma of the mandible in a 47-year-old woman metastasized to the Gasserian ganglion probably through the perineural space of the inferior alveolar nerve. The patient was treated by irradiation after excision of the tumor from the ganglion. She is currently an outpatient in the oral and maxillofacial surgery department; two years and seven months after the first examination, there is no sign of recurrence or metastasis of adenoid cystic carcinoma.     

Enhanced fluoride uptake from mouthrinses

It has been shown in laboratory and animal studies that tooth enamel becomes considerably more reactive toward low levels of fluoride after receiving pre-treatment which forms dicalcium phosphate dihydrate (DCPD) in the enamel as an intermediate. This in vitro study was undertaken to determine the effect on human enamel fluoride uptake of incorporating DCPD-forming rinses into a conventional fluoride rinsing program. In one group, enamel samples received a one-minute rinse with 0.2% NaF each day for 20 days. Samples in the second group were treated identically, except that they were also given a one-minute DCPD-forming rinse prior to the first, sixth, eleventh, and sixteenth fluoride rinses. At the end of the rinsing program, all samples were washed in 1 M KOH to remove labile fluorides. The enamel biopsy data showed that the fluoride uptake resulting from 0.2% NaF alone was not statistically significant, whereas uptake produced by the DCPD-forming plus NaF rinses was significant. The results suggest that the DCPD-forming rinse may improve the efficacy of fluoride rinse programs.     

The relationship between serum IgG levels to subgingival gram-negative bacteria and degree of periodontal destruction

The relationship between the serum IgG antibody titer against seven species of Gram-negative periodontopathic bacteria and clinical parameters (including plaque index, gingival index, periodontal pocket depth, and alveolar bone loss) was studied in 38 subjects. IgG antibody titer against the sonicated antigens was determined by micro-ELISA. A statistically significant correlation was found between the serum antibody titer against B. gingivalis and the degree of clinical parameters, especially pocket depth. The serum IgG levels against the seven micro-organisms in 16 periodontal patients before and after clinical treatment were also determined. Responses to B. gingivalis decreased (p less than 0.001), whereas responses to E. corrodens (p less than 0.01) increased slightly. No marked differences were noted between pre- and post-treatment sera in titers against B. intermedius, B. loescheii, F. nucleatum, A. actinomycetemcomitans, and C. ochracea.     

Relationship between gingival health and dental caries in children aged 7-12 years

The purpose of this study was to investigate the relationship between gingival health and dental caries in elementary school children in Japan. The subjects were 474 children aged 7 to 12 years who attended dental check-ups at an elementary school. The Oral Rating Index for Children, which consists of five categories (+2, +1, 0, -1, -2), was used to rate the findings of the gingival health examination. The dental examination was performed using the WHO caries diagnostic criteria for DMFT. Children were divided into three groups: a healthier group (H-group) made up of those scoring +2 (excellent) or +1 (good), an equivocal group (E-group) made up of those scoring 0, and a gingival less-healthy group (L-group) made up of those scoring -2 (very poor) or -1 (poor). Overall percentages for the H-group, E-group and L-group were 48.3%, 21.5% and 30.2%, respectively. The number in the L-group increased with increasing age. The mean scores of the DT and DMFT in the H-group were significantly lower than those in the L-group (p < 0.01 and p < 0.05, respectively). The results suggest that oral hygiene instruction should be given to children in order to motivate self-care, not only to avoid dental caries but also to prevent gingivitis.     

Finite element analysis of the stresses around fixtures in various reconstructed mandibular models--part II (effect of horizontal load).

AIM OF EXPERIMENT: Having already studied the effect of vertical load (Nagasao et al., 2002), the purpose of this study was to investigate the effect of horizontal load on implants embedded into a virtually reconstructed mandible. MATERIAL AND METHODS: Three-dimensional virtual models of various reconstructed mandibles were designed on a PC and 50 N horizontal loads were applied on the cantilever portion of the upper structure. Then, using a finite element analysis, stresses occurring around the implants were calculated, and the directions of the forces that cause the maximum von Mises stresses were evaluated. Finally, the results were compared with those from vertical loading. RESULTS: In all models, the maximum stresses occurred around the implants embedded on the premolar region of the loaded side. In addition, the locations at which the maximum von Mises stresses occurred were greatly influenced by the structural character of the loaded side. CONCLUSION: When horizontal loads were applied to reconstructed mandibles, the location and direction of the maximum stresses around the dental implants appeared to be influenced much more by the structural characters of the reconstructed mandibles when compared with vertical loads.     

Occlusal phase of gum-chewing strokes

The occlusal phase of chewing is especially interesting because food particles are being pulverized in this phase. For efficient chewing the upper and lower teeth must come together in a congruent fashion with less variation than in other phases. To examine this expectation the chewing motions of 28 women were recorded optoelectrically, and their frontal and sagittal angles of the closing and following opening strokes were measured at 3.0 mm (3-D linear distance) of opening. Closing strokes were more stable than opening strokes. The frontal angle was correlated with the sagittal angle during closing. The opening and closing sagittal angles were moderately correlated, and the opening and closing frontal angles were negatively correlated at the intersubject level. No direct association was found between the closing strokes and following opening strokes at the intra-subject level. These results suggest that closing strokes are more stable than opening strokes, resulting in efficient mastication.     

Novel identification of a four-base-pair deletion mutation in PITX2 in a Rieger syndrome family

Rieger syndrome is one of the most serious causes of tooth agenesis. Mutations in the PITX2, FOXC1, and PAX6 genes have been associated with Rieger syndrome. We have studied a three-generation Chinese family affected with Rieger syndrome and showing prominent dental abnormalities. Mutational screening and sequence analysis of the PITX2 gene revealed a previously unidentified four-base-pair deletion of nucleotides 717-720 in exon 5 in all affected members. The mutation causes a frame shift after Thr44, the 7th amino acid of the homeo-domain, and introduces a premature stop codon in the gene sequence. This deletion is the first unquestionable loss-of-function mutation, deleting all the functionally important parts of the protein. Our novel discovery indicates that the oligodontia and other phenotypes of Rieger syndrome observed in this family are due to this PITX2 mutation, and these data further support the critical role of PIXT2 in tooth morphogenesis.